Preparation of lube hydrocracking stocks

ABSTRACT

A PROCESS FOR PREPARING HIGH V.I. LUBE OILS OF HIGH QUALITY IN IMPROVED YIELD COMPRISING FRACTIONATING THE 720-855*F., (B) 855 TO 980*F. AND (C) THE RESIDUUM OR A FRACTION BOILING AT FROM 986-1070*F., SOLVENT EXTRACTING FRACTION (B) WITH A SOLVENT HAVING PREFERENTIAL SOLUBILITY FOR AROMATICS SUCH AS FURFURAL, RECOMBINING THE THREE FRACTIONS, AND HYDROCRACKING THE COMBINED FRACTIONS AT FROM 720 TO 800*F. USING A HYDROGEN PARTIAL PRESSURE OF FROM 2,000 OT 3,000 P.S.I. THE HIGHER BOILING FRACTION IS DEASPHALTED IF REQUIRED.

United States Patent 3,663,427 PREPARATION OF LUBE HYDROCRACKIN STOCKSJeffrey R. Thomas, Claymont, and lb Steinmetz, 'Wilfiiiiig ABSTRACT onTHE DISCLOSURE A process for preparing high V.I. lube oils of highquality in improved yield comprising fractionating the stock materialinto three fractions, boiling at (a) from 720-855 F., (b) 855 to980; F.and (c) the residuum or a fraction boiling at from 986 -p1070 R, solventextracting fraction (b) ,with a solvent having preferential solubilityfor aromaticstsuch as turfural, recombining the-three I fractions, andhydrocracking the'co'mbined fractions at from 720 to 800 F. using'ahydrogen partial pressure of from 2,000 to.3,000 p.s.i.-.The higherboiling fraction is deasphalted if required.

BACKGROUND OF THE INVENTION In the past various processes have been usedfor up The present invention relates to a hydrocracking process whereinthe feed stock is prepared so as to provide an improved yield of aproduct lube oil having arhigh vis-' cosity index. In general thispreparation involves'jvacuum fractionating an atmospheric residuum intothree lube...

stock streams-which are: I 5. 3

(a) A distillate boiling in the range of 720 (true boilingpointhereinafter TBP).

(b) A distillate boiling from 855 JTBP fto' ai point in the range offrom 980 F. to 1070'F. TBP depending on the particular crude and productlubes, requirements and.

(c) A fraction boiling'above'fraction (b) which may be a distillateboiling at from 980 1070? F. TBP or'a residuum boilingatabove. 1070* F.(TBP). .The fraction (b) is solvent extracted with a solvent havingpreferential solubility for aromatics to produce a dewaxed oil-having aviscosity index 10 to 30 viscosity index units above the dewaxed oilviscosity index of the charge. (As used herein viscosity index or V.I.is determined by ASTM D2270).' The depth of this extraction generally isgreater for lower V.I. charge stocks such as those having a V.I. of 30to 60 than for charge higher V.I. charge stocks such as those having aVI. of from 60 to 90. In general suitable solvents for this extractioninclude furfural, acetophenone, phenol, mixtures of phenol and cumene,acetonitrile, nitrobenzene, aniline, 2,2-dichlorodiethyl ether, dimethylsulfoxide and mixtures thereof. The particular solvent selected isdependent on several considerations such as economics, the depth ofextraction required, and characteristics of the particular crude fromwhich the fraction is derived. Generally furfural and phenol are thepreferred solvents. The temperature at which the extraction is performedmust be below the temperature of miscibility of the oil and the Feesolvent in order to have any extractive separation, and usually is wellbelow the temperature of miscibility for an efiicient operation withgood yields of raffinate. Since the present invention normally does notinvolve dewaxing the charge stock the lower temperature limit forsolvent extraction is that temperature at which solids appear in thestock being solvent extracted. The temperature range encompassing all ofthe suitable operating temperatures for all ofthe suitable solvents isabout 0 to 350 F. In the case of furfural, however, a temperature in therange of about 125 to 3 F. is preferably employed. The ratio of solventto oil to be used is somewhat interdependent on the particulartemperature being used. Generally, solvent to oil ratios in the range of6:1 to 0.25:1 are suitable withratiosof from 4:1 to 08:1 being thepreferred range. The equipment employed in carrying out the solventextraction is not critical and any conventional solvent extractionequipment can be used such as rotating disc contactors, Podbielniakreactors and countercurrent packed bed extraction columns. Either abatch or continuous operation may be used.

When the third component is a vacuum residuum boiling above 1070 F., itshould be deasphalted such as by conventional propane deasphalting toproduce a deasphalted oil-witha. Ramsbottom carbon content of no greaterthan 2.0 wt. percent. In accordance with the presentinventionno-aiurther upgrading of this component is required. Ifthethird component is a distillate, such as that 'boiling'in the rangeof from 960 to 1070 F. no upgrading is required. These components areblended to form a hydrocracker charge containing from 20 to 70 volume"percent of component (a), from to volume percent of the rafiinate ofcomponent (b) and from 10 to 40 vol- 'ume percent of component (c). ,Theblend feed stock is hydrocracked at from 2,000 to 3,000 psi. hydrogenpartial pressure. The hydrocracker iis generally operated at a LH SV(liquid hourly space ivelocity) of from 05 to 1.5. The hydrocracker isbest operatedat aterriperature of from 720 to 800 F. Genboilingabovfe650 P. which is 60 to vol. percent of the hyrocracke'r charge andpreferably greater than 70 vol. percent of the hydrocracker charge. Thisdepends on the precise feed blend prepared and the viscosity index leveldesired.- As the desired viscosity index of the lobes increases less ofcomponent (c) above can be tolerated in the feed blend and more ofcomponent (a) is required.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the examples, Example I isillustrative of the present invention and Examples 2 to 5 illustrate theresults obtained using other refining techniques. In each of Examples lto 5 the crude used in a Lagomedia crude having a gravity, API of 33, asulfur content of 1.2 wt. percent, a viscosity of 54 Saybold universalseconds at F., a pour point of 0 F. and an O.D color of 21,000. In eachof the extractions in the examples is carried out using furfural in avolume solvent to oil ratio of 1.5 to 1.0 at 220 F. The properties ofthe various components as used in Examples 1, 3, 4, and 5 are reportedin Table I.

erany'anysmfaetive hydrogenation catalyst can be used- TABLE I Compo-Component B Component nent A,

unex- Unex- Unextracted tracted Extracted traeted Extracted API gravityat 60 F 25. 7 26. 1 27.6 19. 2 25. 8 Initial boiling point, F 686 815652 589 624 50% point, F 777 923 923 998 1002 End point/recoveryViscosity at 210 F., Cst 5. 2 15. 5 11. 4 26 18.8

842 F./98%; 9 992 F./98%; a 993 F./98%; 4 1,030 F./78%.

The properties of the components used in Example II are reported inTable II. (Both components are unextracted) TABLE II Compo- Component Anent B API gravity at 60 F. 26. 2 23. 2 Initial boiling point, F. 670717 50% boiling point, F... 791 908 End point/recovery Viscosity at 210F., Cst 5. 32 11. 97

of asphatic compounds toform a hydrocracker feedstock and catalyticallyhydrocracking said hydrocracker feed stock at from about 720 to 800 F.,a hydrogen partial pressure of from 2,000 to 3,000 pounds per squareinch.

2. The process of claim 1 wherein fraction (0) boils at from about 980F. to 1070 F.

3. The process of claim 2 wherein the solvent extraction is carried outusing a ratio of solvent to oil from 4 to 1 to 0.8 to 1.

4. The process of claim 3 wherein the solvent is furfural.

5. The process of claim 4 wherein the solvent extraction is carried outat from 125 F. to 325 F.

6. The process of claim 5 wherein fraction (a) constitutes from 20 to 70volume percent of the hydrocracker charge stock, the r'afllnate offraction (b) constitutes from to 50 volume percent of the hydrocrackerfeed stock, and fraction (0) constitutes from 10 to volume percent ofthe hydrocracker feed stock.

TABLE 111 Example 1 2 3 4 5 Example 1 2 3 4 5 Feed preparation:

Unextraeted Component A, volume percent 28. 1 64.0 63. 4 26.5 63.7Unextraeted Component 13, volume percent- 36.0 37. 4 Extracted ComponentB, volume percent. 45. 8 36.4 13.4 13.4 Unextracted Component 0, volumepercent- 26. 1 Extracted Component 0, volume percent 22.8 22.8Hydrocracked lube, volume percent charge 62. 0 55. 7 56. 9 53. 1 54. 0Operating conditions:

Catalyst temperature, F-.. 770 779 760 780 765 LHSV, vol./hr./vol 0. 920. 08 0. 88 0. 89 1. 21 Hz partial pressure, p.s.i.g 2, 500 2, 550 2,500 2, 500 2, 500 Reactor gas rate, s.e.f./bbl 4, 389 4, 609 4, 715 4,247 Lube grade V.I.s:

70 neutral 83 82 91 91 92 100 neutral- 100 102 100 101 100 107 100 10395 98 95 As can be seen from Table IH the present invention asillustrated in Example I results in a substantially improved yield whilemaintaining a high viscosity index in the various lube fractions.

We claim:

1. A process for the preparation of lube oils comprising fractionating acrude into a fraction (a) boiling principally at from about 720 F. to855 F., a fraction (b) boiling principally at from about 855 F. to from980 to 1070 F. and a fraction (c) boiling above fraction (b) solventextracting fraction (b) with a solvent having a preferential solubilityfor aromatic compounds, combining this rafiinate with the other twofractions which frac- 7. The process of claim 6 wherein thehydrocracking catalyst is sulfided nickel-tungsten.

8. The process of claim 7 wherein the catalyst is supported onsilica-alumina.

References Cited UNITED STATES PATENTS tions contain their originalaromatic compounds exclusive 20818, 93

